1. Field of the Invention
This invention generally relates to an electronic circuit device, and in particular, relates to an electronic circuit device in which a DC bias is applied to two transistors in series.
2. Description of the Related Art
An oscillator is used in a device using a high frequency wave such as a communication device. It is difficult to manufacture a high-performance oscillator using a high frequency wave such as a milliwave. There is a case where a signal of relatively low frequency from the oscillator is multiplied into a second harmonic wave and a third harmonic wave by a frequency multiplier and is used. The frequency multiplier is a circuit that outputs a distorted waveform including a nonlinear signal such as a higher harmonic component (a second harmonic wave or a third harmonic wave) and outputs a signal of desirable frequency (a second harmonic wave or a third harmonic wave) through a filter. Japanese Patent Application Publication No. 2000-156611 discloses a frequency multiplier using a transistor.
Generally, an electrical power of a high frequency component is smaller than that of a reference wave, in a frequency multiplier. A multiplication loss is therefore generated with respect to the reference wave. And an insertion loss of a filter is generated when the filter is used. Therefore, a signal level is reduced when the frequency multiplier multiplies an output signal from the oscillator. And so, an amplifier is provided at the backside of the frequency multiplier, when the frequency multiplier is used. In this case, a size of the circuit is enlarged. For example, a chip size is enlarged when the circuit is a MMIC (Microwave Monolithic Integrated Circuit).